JPH0774845B2 - Elliptical jacket type polarization-maintaining optical fiber - Google Patents
Elliptical jacket type polarization-maintaining optical fiberInfo
- Publication number
- JPH0774845B2 JPH0774845B2 JP63172568A JP17256888A JPH0774845B2 JP H0774845 B2 JPH0774845 B2 JP H0774845B2 JP 63172568 A JP63172568 A JP 63172568A JP 17256888 A JP17256888 A JP 17256888A JP H0774845 B2 JPH0774845 B2 JP H0774845B2
- Authority
- JP
- Japan
- Prior art keywords
- optical fiber
- polarization
- refractive index
- polarizer
- wavelength
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/105—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type having optical polarisation effects
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)
Description
【発明の詳細な説明】 [産業上の利用分野] 本発明は光ファイバ偏光子として用いるのに適した楕円
ジャケット型偏波面保存光ファイバに関する。TECHNICAL FIELD The present invention relates to an elliptical jacket type polarization-maintaining optical fiber suitable for use as an optical fiber polarizer.
[従来の技術] 偏波面保存光ファイバにより偏光子を構成するために
は、直交する2つの固有偏波モードのうち一方のモード
を遮断状態とする絶対単一偏波動作を示す光ファバ(絶
対単一偏波面保存光ファイバ)を用いることが望まし
い。この点に関し、本出願人は特願昭61-124663号明細
書、特願昭61-124664号明細書及び特願昭61-203751号明
細書において、それぞれ第6図(a)〜(c),第7図
(a)〜(c)及び第8図(a)〜(c)に示すような
絶対単一偏波面保存光ファイバ(SPF)を提案してい
る。[Prior Art] In order to construct a polarizer with a polarization-maintaining optical fiber, an optical fiber (absolute single polarization operation that exhibits an absolute single polarization operation in which one of two orthogonal polarization modes is cut off. It is desirable to use a single polarization maintaining fiber. With respect to this point, the applicant of the present invention discloses in Japanese Patent Application No. 61-124663, Japanese Patent Application No. 61-124664 and Japanese Patent Application No. 61-203751 each of FIGS. 6 (a) to (c). , (A) to (c) of FIG. 7 and (a) to (c) of FIG. 8 have proposed an absolute single polarization maintaining fiber (SPF).
第6図(a)〜(c)に示した光ファイバ61は、楕円ジ
ャケット62の短軸側においてはMC(マッチド クラッ
ド)型の屈折率分布を、長軸側においてはW型の屈折率
分布をそれぞれ形成したものであり、基本モードのカッ
トオフ波長がMC型には存在せず、W型には存在すること
を利用して、絶対単一偏波動作(ASP動作)を可能とし
ている。The optical fiber 61 shown in FIGS. 6A to 6C has an MC (matched cladding) type refractive index distribution on the minor axis side of the elliptical jacket 62 and a W type refractive index distribution on the major axis side. By utilizing the fact that the cutoff wavelength of the fundamental mode does not exist in the MC type but does exist in the W type, absolute single polarization operation (ASP operation) is possible.
一方、第7図(a)〜(c)に示した光ファイバ71は楕
円ジャケット72の短軸側及び長軸側ともW型の屈折率分
布を形成しているが互いに溝の深さに違いを持たせたも
のである。W型ファイバでは溝の深さによって単一モー
ド動作域が決定されるので、溝の深さに違いを持たせた
ことにより短軸側及び長軸側に偏波したモードの単一モ
ード動作域が異なり、一方は低損失な導波モード、他方
は高損失な漏洩モードとなる動作域が存在し、これを利
用して絶対単一偏波動作を可能としている。On the other hand, the optical fiber 71 shown in FIGS. 7A to 7C has a W-shaped refractive index distribution on both the short axis side and the long axis side of the elliptical jacket 72, but the groove depths are different from each other. It has a. Since the single-mode operating range is determined by the groove depth in W-type fiber, the single-mode operating range of the modes polarized on the minor axis side and the major axis side is determined by making the groove depth different. However, there is an operating region in which one is a low-loss guided mode and the other is a high-loss leaky mode, and this is utilized to enable absolute single polarization operation.
更に、第8図(a)〜(c)に示した光ファイバ81は、
これら第6図(a)〜(c)及び第7図(a)〜(c)
に示す光ファイバでは、楕円ジャケット62及び72の屈折
率分布をその円周方向に分割して短軸方向と長軸方向の
各屈折率を異なったものとする必要があるため、製造が
難しく設計値通りの光ファイバを得る歩留りが悪かった
点を改善したものである。即ち、コア1を中心として、
その外周部に順次クラッド2,楕円ジャケット3及びサポ
ー4を設けた4槽構造の偏波面保存光ファイバにおい
て、楕円ジャケット3がクラッド2より低い屈折率を有
すると共に、サポート4が上記クラッド2と等しい屈折
率を有し、楕円ジャケット3が25〜40%の楕円率とクラ
ッド2に対して−0.05〜−0.03%の比屈折率を有する構
成としたものである。楕円ジャケット3がその短軸方向
及び長軸方向に同一の屈折率を有してしているので、容
易に製造することができる利点を有する。Furthermore, the optical fiber 81 shown in FIGS.
6 (a) to (c) and 7 (a) to (c).
In the optical fiber shown in Fig. 2, it is necessary to divide the refractive index distribution of the elliptical jackets 62 and 72 in the circumferential direction so that the respective refractive indexes in the minor axis direction and the major axis direction are different, so that it is difficult to manufacture. This is an improvement in that the yield for obtaining an optical fiber of the desired value was poor. That is, with the core 1 as the center,
In a polarization-maintaining optical fiber having a four-chamber structure in which a clad 2, an elliptical jacket 3 and a support 4 are sequentially provided on the outer periphery thereof, the elliptical jacket 3 has a lower refractive index than the clad 2, and the support 4 is equal to the clad 2. The elliptical jacket 3 has a refractive index of 25 to 40% and the relative refractive index of the cladding 2 is -0.05 to -0.03%. Since the elliptical jacket 3 has the same refractive index in the minor axis direction and the major axis direction, it has an advantage that it can be easily manufactured.
しかし、上記した第6図、第7図、第8図の楕円ジャケ
ット型偏波面保存光ファイバは、モード複屈折率の効果
を考慮していなかったので、偏光子としての構造が最適
化されておらず、従って、その特性、例えば消光比、挿
入損失等も最良とはいい得なかった。However, since the elliptic jacket type polarization-maintaining single-mode optical fibers of FIGS. 6, 7, and 8 described above do not consider the effect of the mode birefringence, the structure as a polarizer is optimized. Therefore, the characteristics, such as extinction ratio and insertion loss, cannot be said to be the best.
この点に鑑み、本出願人は、未だ公知ではないが、モー
ド複屈折率をも考慮することにより、偏光子として適し
た絶対単一偏波動作を示す楕円ジャケット型偏波面保存
光ファイバを、既に提案している(特願昭62-318967
号)。これは、コアを中心としてその外周部に順次クラ
ッド、楕円ジャケット及びサポートが設けられている4
層構造の偏波面保存光ファイバにおいて、クラッドとサ
ポートの屈折率がシリカの値と同じで、クラッドに対す
るコアの比屈折率差Δ+を0.3%以下、クラッドに対す
る楕円ジャケットの比屈折率差Δ−を−0.15〜−0.25
%、モード複屈折率Bを4.52×10-4以上として、楕円ジ
ャケット型偏波面保存光ファイバを構成したものであ
る。In view of this point, the present applicant has not yet publicly known, but by considering the mode birefringence, an elliptical jacket type polarization-maintaining optical fiber showing an absolute single polarization operation suitable as a polarizer, I have already proposed (Japanese Patent Application No. Sho 62-318967)
issue). This has a clad, an elliptical jacket, and a support, which are sequentially provided around the core around the core.
In a polarization-maintaining optical fiber with a layered structure, the refractive index difference between the clad and the support is the same as that of silica, the relative refractive index difference Δ + of the core to the clad is 0.3% or less, and the relative refractive index difference Δ− of the elliptical jacket to the clad is −. −0.15 to −0.25
%, And the mode birefringence B is 4.52 × 10 −4 or more, and an elliptical jacket type polarization-maintaining optical fiber is constructed.
上記は、偏波面保存光ファイバのモード複屈折率を考慮
した有限要素法により、ある特定の波長、曲げ半径、巻
き付け長さで、偏波面保存光ファイバの直交する2つの
偏波の曲げ損失特性に大きな差が生ずるよう構造パラメ
ータを決める。通常、半導体レーザ光源で、消光比(円
偏波入射時)−40dB以下、挿入損失(x偏波、楕円の長
軸に偏波したモード)0.5dB以下の特性が得られてい
る。The above is the bending loss characteristics of two orthogonal polarizations of a polarization-maintaining optical fiber at a specific wavelength, bending radius, and winding length by the finite element method considering the mode birefringence of the polarization-maintaining optical fiber. The structural parameters are determined so that there is a large difference. In general, a semiconductor laser light source has characteristics of extinction ratio (when circularly polarized wave is incident) of -40 dB or less and insertion loss (x-polarized wave, a mode polarized on the long axis of an ellipse) of 0.5 dB or less.
[発明が解決しようとする課題] しかしながら、絶対単一偏波動作域、即ち偏光子として
機能する波長域が狭いため、例えば波長0.85μmでは動
作するが、0.81μmというように中心波長がずれた光源
では特性が悪くなるという問題がある。[Problems to be Solved by the Invention] However, since the absolute single polarization operation range, that is, the wavelength range functioning as a polarizer is narrow, the operation is performed at a wavelength of 0.85 μm, but the center wavelength is deviated from 0.81 μm There is a problem that the characteristics are deteriorated in the light source.
最も重要な問題は、回転角速度センサ用光源として最も
適しているSLD(スーパルミネッセントダイオード)の
場合、そのスペクトル幅が広いため、絶対単一偏波動作
の中心波長とSLDの中心波長がずれていて、そのスペク
トル幅が絶対単一偏波動作域よりはみ出している場合、
挿入損失の増加、消光比の劣化が生ずる。この場合は、
絶対単一偏波動作域の中心波長とSLDの中心波長を一致
させる必要があるが、SLDの中心波長はメーカにより異
なったり、スペクトル幅がSLDの注入電流により変化す
ることから、それに合った偏光子をそのつど製造しなけ
ればならない。The most important problem is that in the case of the SLD (super luminescent diode), which is the most suitable light source for the rotation angular velocity sensor, its central wavelength is deviated from the central wavelength of the SLD because the spectrum width is wide. And its spectral width is outside the absolute single polarization operating range,
Insertion loss increases and extinction ratio deteriorates. in this case,
It is necessary to match the center wavelength of the absolute single-polarization operating region with the center wavelength of the SLD, but the center wavelength of the SLD differs depending on the manufacturer, and the spectrum width changes depending on the injection current of the SLD. You have to make a child each time.
本発明は、偏光子を構成した場合にその偏光子として機
能する波長域が広く、従って絶対単一偏波動作の中心波
長が任意に選定できる楕円ジャケット型偏波面保存光フ
ァイバを提供することにある。The present invention is to provide an elliptical jacket type polarization-maintaining optical fiber having a wide wavelength range that functions as a polarizer when the polarizer is configured, and thus the center wavelength of absolute single polarization operation can be arbitrarily selected. is there.
[課題を解決するための手段] 本発明の楕円ジャケット型偏波面保存光ファイバは、コ
アを中心としてその外周部に順次クラッド、楕円ジャケ
ット及びサポートが設けられている4層構造を持ち、曲
げを印加して実効的に絶対単一偏波動作が可能となる偏
波面保存光ファイバにおいて、中央に対し条長15mの範
囲で外径が±20〜30μmの間で変化するように、光ファ
イバ外径を連続的に一様に変化させて構成したものであ
る。[Means for Solving the Problems] An elliptical jacket type polarization-maintaining single-mode optical fiber of the present invention has a four-layer structure in which a clad, an elliptical jacket, and a support are sequentially provided around a core as a center and are bent. In a polarization-maintaining single-mode fiber that can be effectively applied with absolute single-polarization operation, the outside diameter of the optical fiber should be adjusted so that the outer diameter changes within ± 20 to 30 μm within a strip length of 15 m from the center. The diameter is continuously and uniformly changed.
[作用] 光ファイバ外径が、中央に対し条長15mの範囲で外径が
±20〜30μmの間で変化するように連続的に一様に変化
しているため、光偏光子に適用した場合、波長がずれて
もそれらの波長全てに対して絶対単一偏波動作が可能と
なる。従って、光源としてスペクトル幅の広いSLDを用
い、絶対単一偏波動作の中心波長とSLDの中心波長がず
れていても、絶対単一偏波動作の中心波長を任意に変え
られるので、SLDのスペクトル幅が絶対単一偏波動作域
よりはみ出さなくなり、挿入損失の増加、消光比の劣化
をなくすことができる。[Operation] Since the outer diameter of the optical fiber changes continuously and uniformly so that the outer diameter changes within ± 20 to 30 μm in the range of the strip length of 15 m from the center, it was applied to the optical polarizer. In this case, even if the wavelengths are deviated, absolute single polarization operation is possible for all those wavelengths. Therefore, even if the center wavelength of the absolute single polarization operation and the center wavelength of the SLD are deviated by using the SLD with a wide spectrum width as the light source, the center wavelength of the absolute single polarization operation can be arbitrarily changed. The spectrum width does not extend beyond the absolute single polarization operating range, so that increase in insertion loss and deterioration of extinction ratio can be eliminated.
[実施例] 以下、本発明を図面に従って説明する。EXAMPLES The present invention will be described below with reference to the drawings.
第3図(a)(b)(c)はそれぞれ本発明の実施例の
前提となる絶対単一偏波面保存光ファイバの横断面図、
X軸方向の屈折率分布図およびY軸方向の屈折率分布図
である。図中、1はGeが添加されたSiO2ガラスからなる
コア、2はコア1の外周部を囲繞する純粋SiO2ガラスか
らなるクラッド、3はクラッド2の外周部を囲繞する楕
円ジャケット3である。この楕円ジャケット3は、B2O3
を添加したSiO2ガラスからなりクラッド2の屈折率より
低い屈折率を有している。この楕円ジャケット3の外周
部には、これを囲繞するように、純粋SIO2ガラスからな
りクラッド2と等しい屈折率を有するサポート4が設け
られている。3 (a), (b), and (c) are transverse sectional views of an absolute single polarization-maintaining single-mode optical fiber which is the premise of the embodiment of the present invention, respectively.
It is a refractive index distribution map of an X-axis direction, and a refractive index distribution map of a Y-axis direction. In the figure, 1 is a core made of SiO 2 glass to which Ge is added, 2 is a clad made of pure SiO 2 glass surrounding the outer periphery of the core 1, and 3 is an elliptical jacket 3 surrounding the outer periphery of the clad 2. . This oval jacket 3 is made of B 2 O 3
It is made of SiO 2 glass to which is added and has a refractive index lower than that of the cladding 2. A support 4 made of pure SIO 2 glass and having a refractive index equal to that of the cladding 2 is provided on the outer peripheral portion of the elliptical jacket 3 so as to surround it.
第3図(a)(及び(c)において、aはコア1の半
径、bcは楕円ジャケット3の長軸半径、btは楕円ジャケ
ット3の短軸半径であり、クラッド2の半径はクラッド
厚とコア半径の比をδとして(1+δ)aで表わしてあ
る。n(r)はコア1、クラッド2、楕円ジャケット3
及びサポート4の屈折率が、中心Oからの距離rの関数
で表わされることを示す。Δ+はクラッド2に対するコ
ア1の比屈折率差、Δ−クラッド2に対する楕円ジャケ
ット3の比屈折率差である。3 (a) (and (c), a is the radius of the core 1, bc is the major axis radius of the elliptical jacket 3, bt is the minor axis radius of the elliptical jacket 3, and the radius of the cladding 2 is the cladding thickness. The ratio of the core radii is represented by δ, and is represented by (1 + δ) a, where n (r) is the core 1, the clad 2, and the elliptical jacket 3.
And the refractive index of the support 4 is expressed as a function of the distance r from the center O. Δ + is the relative refractive index difference of the core 1 with respect to the cladding 2, and the relative refractive index difference of the elliptical jacket 3 with respect to the Δ− cladding 2.
屈折率分布n(r)の溝の深さ、即ちΔ−は、楕円ジャ
ケット3の短軸および長軸側で同じであり、同シリカに
対し比屈折率差Δ−を−0.15〜−0.25%の範囲で定め
る。また、屈折率分布n(r)の溝の幅は、楕円ジャケ
ット3の楕円率εを25〜40%の範囲で定める。The groove depth of the refractive index distribution n (r), that is, Δ− is the same on the minor axis side and the major axis side of the elliptical jacket 3, and the relative refractive index difference Δ− is −0.15 to −0.25% with respect to the silica. Determined within the range of. Further, the width of the groove having the refractive index distribution n (r) is determined so that the ellipticity ε of the elliptical jacket 3 is in the range of 25 to 40%.
かかる構成を前提として、モード複屈折率Bの作用効果
を考慮しつつ、偏光子として最適な構造を、有限要素法
により計算機により理論解析する。この理論解析では、
便宜上、楕円ジャケット3の部分までをコアであるとし
て扱い、この実効コア部内の正規化位相定数Uと、その
周囲のサポート4を実効クラッド部として扱ったときの
正規化横方向減衰定数Wとを吟味する。Based on such a configuration, the optimum structure of the polarizer is theoretically analyzed by a computer by the finite element method while considering the effect of the mode birefringence B. In this theoretical analysis,
For convenience, the part up to the elliptical jacket 3 is treated as a core, and the normalized phase constant U in this effective core portion and the normalized lateral damping constant W when the support 4 around it is treated as an effective cladding portion. Scrutinize.
詳述するに、まず実効コア部としての楕円の長軸(x
軸)、短軸(y軸)の屈折率分布より、x軸方向に電界
を持つx偏波とy軸方向に電界を持つy偏波とに関し、
それぞれ進行方向の伝搬定数βx,βyを求める。この両
者の差Δβ=β x −βyは、屈折率分布の非軸対称性及
び異方性歪により生じるx偏波、y偏波間の伝搬定数差
であり、この伝搬定数差Δβはできるだけ大きいことが
望まれる。正規化モード複屈折率Bと伝搬定数差Δβ及
び結合長CLの間には、次の関係があり、両モード間の結
合を減らすことができるからである。To elaborate, first, the major axis of the ellipse (x
Axis) and a minor axis (y-axis) refractive index distribution, regarding x-polarized waves having an electric field in the x-axis direction and y-polarized waves having an electric field in the y-axis direction,
The propagation constants βx and βy in the traveling direction are obtained. The difference Δβ = β x −βy between the two is a propagation constant difference between the x polarization and the y polarization caused by the non-axial symmetry of the refractive index distribution and the anisotropic distortion, and this propagation constant difference Δβ should be as large as possible. Is desired. This is because the normalized mode birefringence B, the propagation constant difference Δβ, and the coupling length CL have the following relationship, and the coupling between both modes can be reduced.
但し、k0(≡2π/λ)は自由空間の光の波数、λは自
由空間中の光の波長である。 However, k 0 (≡2π / λ) is the wave number of light in free space, and λ is the wavelength of light in free space.
次に、これらの値βx,βy,Δβを用いて、x偏波の実効
コア部内の正規化位相定数Uxと、y偏波の実効コア部内
の正規化位相定数Uyとを次式にて求める。Next, using these values βx, βy, and Δβ, the normalized phase constant Ux in the effective core part of the x polarization and the normalized phase constant Uy in the effective core part of the y polarization are calculated by the following equations. .
但し、n0は実効コア部内の中心(r=0)での屈折率で
ある。 However, n 0 is the refractive index at the center (r = 0) in the effective core portion.
一方、x偏波、y偏波の実効クラッド部(サポート部)
内の正規化横方向減衰定数Wx,Wyは、上記(1),
(2)式の正規化位相定数Ux,Uyと正規化周波数Vx,Vyと
を用いて、それぞれ次式で求められる。On the other hand, x-polarization and y-polarization effective cladding (support)
The normalized lateral damping constants Wx and Wy in the above are (1),
Using the normalized phase constants Ux, Uy and the normalized frequencies Vx, Vy of the equation (2), they are respectively calculated by the following equations.
但し、正規化周波数Vx,Vyは、実効コア部内の屈折率
n0、自由空間中の波数k0、長軸半径bc、短軸半径bt、実
効クラッド部に対する実効コア部の比屈折率差Δの関数
で表わされ、 で定義されている。 However, the normalized frequencies Vx and Vy are the refractive indices in the effective core.
n 0 , wave number in free space k 0 , major axis radius bc, minor axis radius bt, expressed as a function of relative refractive index difference Δ of the effective core portion with respect to the effective cladding portion, Is defined in.
従って、偏光子としての最適化を図る上で問題となる曲
げ損失特性は、上記(1)〜(6)式の緒量U ,W ,V
(=x,y)を基にして、有限要素法により電磁界分
布を知ることにより計算で求めることができ、又そのと
きの屈折率分布をRNF(Refracted Near Field)により
測定し、これにより構成パラメータを求めることができ
る。Therefore, there is a problem in the optimization of the polarizer.
The loss characteristic is the amount U of the above equations (1) to (6). , W , V
Based on (= x, y), the electromagnetic field component is calculated by the finite element method.
By knowing the cloth, it can be calculated, and
The refractive index distribution of mushrooms by RNF (Refracted Near Field)
You can measure and use this to determine the configuration parameters
It
第4図の実線は上記理論解析法による計算により得られ
た曲げ損失特性を示し、黒丸のプロットはx偏波の曲げ
損失の実測値を、白丸プロットはy偏波の曲げ損失の実
測値を示す。これから上記理論解析法による曲げ損失特
性は実測曲げ損失特性と極めて近似していることが判
る。よって、上記理論解析法により所望の曲げ損失特性
の楕円ジャケット型偏波面保存光ファイバを計算するこ
とができ、偏光子として最適となる屈折率分布も求める
ことができる。The solid line in FIG. 4 shows the bending loss characteristics obtained by the calculation by the theoretical analysis method. The black circle plots show the measured bending loss values of x polarization, and the white circle plots show the measured bending loss values of y polarization. Show. From this, it can be seen that the bending loss characteristics obtained by the above theoretical analysis method are very similar to the measured bending loss characteristics. Therefore, the elliptic jacket type polarization-maintaining optical fiber having a desired bending loss characteristic can be calculated by the above theoretical analysis method, and the refractive index distribution that is optimum as a polarizer can also be obtained.
上記解析法を用いて、λが1.55,1.30,0.85μmの各波長
用に設計した理論上の曲げ損失特性を第5図に、そのと
きの導波構造を表1に示す。FIG. 5 shows theoretical bending loss characteristics designed for the respective wavelengths of λ of 1.55, 1.30 and 0.85 μm by using the above analysis method, and Table 1 shows the waveguide structure at that time.
但し、正規化モード複屈折率Bは6.34×10-4とし、ま
た、で示す波長1.55μm用、で示す波長1.30μm
用、で示す波長0.85μm用のいずれの光ファイバも、
正規化周波数は、 9<Vx<11, 3.5<Vy<5.55 の範囲にある。 However, the normalized mode birefringence B is set to 6.34 × 10 −4, and the wavelength is 1.55 μm, and the wavelength is 1.30 μm.
, For any wavelength 0.85μm optical fiber,
The normalized frequency is in the range of 9 <Vx <11, 3.5 <Vy <5.55.
第5図の曲げ損失特性から、いずれの光ファイバ
も、曲げ半径が40mm以下ではy偏波の曲げ損失αyがα
y>1dB/mとなる。従って、40mm以下の半径でこの光フ
ァイバを巻けば、実効的にx偏波のみとなり、所望の最
適な光ファイバ偏光子が得られる。From the bending loss characteristics shown in Fig. 5, the bending loss αy of the y-polarized light is α when the bending radius is 40 mm or less.
y> 1 dB / m. Therefore, if this optical fiber is wound with a radius of 40 mm or less, only the x-polarized wave is effectively formed, and a desired optimum optical fiber polarizer can be obtained.
例えば、実際に0.85μm用の光ファイバを曲げ半径40
mmで15回だけ(長さ3.8m)巻回すれば、消光比−47dB
(円偏波入射)、挿入損失0.3dB(x偏波入射)の特性
を有する光ファイバ偏光子が得られる。For example, actually bend an optical fiber for 0.85 μm with a bending radius of 40
Extinction ratio of -47 dB if wound only 15 times (3.8 m in length) in mm
An optical fiber polarizer having characteristics of (circularly polarized wave incident) and insertion loss of 0.3 dB (x polarized wave incident) can be obtained.
上記設計例の光ファイバは、それぞれ曲げ半径40
mm以下で偏光子となるが、これ以外の場合でも、次のよ
うな条件下で偏光子としての構造を最適化できる。即
ち、クラッドとサポートの屈折率がシリカの値と同じ場
合において、クラッド2に対するコア1の比屈折率差Δ
+を0.3%以下、クラッド2に対する楕円ジャケット3
の比屈折率差Δ−を−0.15〜−0.25%、モード複屈折率
Bを4.52×10-4以上とした楕円ジャケット型偏波面保存
光ファイバである。この数値範囲における光ファイバ
も、曲げ半径が或る値以下で偏光子となる。従ってその
偏光子となる曲げ半径は40mmより大きい場合も存在す
る。Each of the optical fibers in the above design example has a bending radius of 40
Although it becomes a polarizer at mm or less, even in other cases, the structure as a polarizer can be optimized under the following conditions. That is, when the refractive index of the clad and the support is the same as that of silica, the relative refractive index difference Δ of the core 1 with respect to the clad 2 is Δ.
+ Is 0.3% or less, elliptical jacket 3 for clad 2
Is an elliptic jacket type polarization-maintaining optical fiber having a relative refractive index difference Δ− of −0.15 to −0.25% and a mode birefringence B of 4.52 × 10 −4 or more. An optical fiber in this numerical range also becomes a polarizer when the bending radius is a certain value or less. Therefore, the bending radius of the polarizer may be larger than 40 mm.
第1図は、上記技術を用いて得られた光ファイバ偏光子
(曲げ半径25mm、巻き付け条長2.4m)の損失波長特性
(測定例)であり、Δλは偏光子として機能する波長幅
を示す。但し、光ファイバ外径は125μmである。FIG. 1 is a loss wavelength characteristic (measurement example) of an optical fiber polarizer (bending radius 25 mm, winding length 2.4 m) obtained by using the above technique, and Δλ represents a wavelength width that functions as a polarizer. . However, the outer diameter of the optical fiber is 125 μm.
上記光ファイバ外径が125μmの例では、絶対単一偏波
動作の中心波長は1.29μmで1.27〜1.31μmの範囲で、
偏光子の機能を有する。波長1.29μmでは消光比−41d
B、挿入損失0.5dBである。波長1.31μm以上では、例え
ば波長1.33μmでは、絶対単一偏波動作は可能である
が、挿入損失が大きくなる。波長1.27μm以下では、Y
偏波が十分減衰しておらず消光比特性が劣化するため
に、絶対単一偏波動作は不可能となる。In the example of the above optical fiber outer diameter of 125 μm, the central wavelength of absolute single polarization operation is 1.29 μm and the range of 1.27 to 1.31 μm
It has the function of a polarizer. Extinction ratio of -41d at wavelength 1.29μm
B, insertion loss is 0.5 dB. At a wavelength of 1.31 μm or more, for example, at a wavelength of 1.33 μm, absolute single polarization operation is possible, but the insertion loss becomes large. At wavelengths below 1.27 μm, Y
Absolute single polarization operation becomes impossible because the polarization is not sufficiently attenuated and the extinction ratio characteristic deteriorates.
第2図は、同一母材より線引きして光ファイバ外径を変
えたときの損失波長特性を示す。一点鎖線は光ファイバ
外径を100μmとしたときの損失波長特性を、実線は光
ファイバ外径を125μmとしたときの損失波長特性を、
点線は光ファイバ外径を150μmとしたときの損失波長
特性を示す。FIG. 2 shows the loss wavelength characteristic when the outer diameter of the optical fiber is changed by drawing the same preform. The one-dot chain line shows the loss wavelength characteristic when the outer diameter of the optical fiber is 100 μm, and the solid line shows the loss wavelength characteristic when the outer diameter of the optical fiber is 125 μm.
The dotted line shows the loss wavelength characteristic when the outer diameter of the optical fiber is 150 μm.
第2図から分るように、絶対単一偏波動作の波長域は、
光ファイバ外径が細いときは短軸側に、太いときは長軸
側にシフトしている。従って、条長15mの範囲で光ファ
イバ外径をデーパ状に連続的に一様に変化させておけ
ば、巻き付け条長は、高々2〜3mも有ればよいので、絶
対単一偏波動作の中心波長を使用する光源の中心波長に
合わせた光ファイバ偏光子が実現できる。As can be seen from FIG. 2, the wavelength range of absolute single polarization operation is
When the outer diameter of the optical fiber is thin, it is shifted to the short axis side, and when it is thick, it is shifted to the long axis side. Therefore, if the outer diameter of the optical fiber is continuously and evenly changed in the range of a strip length of 15 m, the winding strip length may be at most 2 to 3 m. An optical fiber polarizer that matches the center wavelength of a light source using the center wavelength of can be realized.
実際に光ファイバ条長15mの範囲で、光ファイバ外径を
長さ方向中央部で125μm、これから前後方向に±25μ
mの間で外径を徐々に連続的に変化させた偏波面保存光
ファイバを製造し、これを光ファイバ偏光子に適用して
検討した結果、任意に偏光子としての動作中心波長が選
べた。Actually, the optical fiber outer diameter is 125 μm at the center in the longitudinal direction within the range of 15 m, and ± 25 μ in the front-back direction.
We manufactured a polarization-maintaining optical fiber whose outer diameter was gradually and continuously changed between m and applied it to an optical fiber polarizer. As a result, we could select the operation center wavelength as a polarizer. .
[発明の効果] 以上のように、本発明の楕円ジャケット型偏波面保存光
ファイバは、偏光子に適用した場合、動作中心波長が任
意に選定できる偏光子となるので、光源の中心波長がバ
ラツイていても、その光源に対応して動作することがで
きる。その意味で特性歩留まりが向上し、偏光子の低コ
スト化が図れる。[Effects of the Invention] As described above, when the elliptical jacket type polarization-maintaining optical fiber of the present invention is applied to a polarizer, it becomes a polarizer whose operation center wavelength can be arbitrarily selected, so that the center wavelength of the light source varies. However, it can operate corresponding to the light source. In that sense, the characteristic yield is improved, and the cost of the polarizer can be reduced.
回転角度センサの光源であるSLDの中心波長と、偏光子
としての動作中心波長とを合わせることができるため、
従来問題であった特性劣化(挿入損失の増加、消光比の
劣化)がないため、偏光子を使用する各種の機器、例え
ば光ファイバジャイロの如き回転角度センサの特性向上
につながる。Since it is possible to match the center wavelength of the SLD, which is the light source of the rotation angle sensor, with the operation center wavelength of the polarizer,
Since there is no characteristic deterioration (increased insertion loss, deterioration of extinction ratio) which has been a problem in the past, it leads to improvement of characteristics of various devices using a polarizer, for example, a rotation angle sensor such as an optical fiber gyro.
第1図は光ファイバ径125μmの場合の光ファイバ偏光
子の損失波長特性例を示す図、第2図は第1図と同一母
材から得た光ファイバの外径を100μmと150μmとした
場合の光ファイバ偏光子の損失波長特性例を示す図、第
3図(a)(b)(c)はそれぞれ楕円ジャケット型偏
波面保存光ファイバの横断面図、x軸方向の屈折率分布
図及びy軸方向の屈折率分布図、第4図はx偏波及びy
偏波の計算と実測による曲げ損失特性を示す図、第5図
は計算により求めた3種の光ファイバの曲げ損失特性を
示す図、第6図、第7図、第8図はそれぞれ既に提案さ
れている光ファイバの屈折率分布を示す説明図である。 図中、1はコア、2はクラッド、3は楕円ジャケット、
4はサポートである。Fig. 1 is a diagram showing an example of loss wavelength characteristics of an optical fiber polarizer when the optical fiber diameter is 125 µm, and Fig. 2 is a case where the outer diameters of optical fibers obtained from the same base material as in Fig. 1 are 100 µm and 150 µm. Showing an example of loss wavelength characteristics of the optical fiber polarizer of FIG. 3, FIGS. 3 (a), 3 (b) and 3 (c) are cross-sectional views of an elliptical jacket type polarization-maintaining optical fiber, a refractive index distribution diagram in the x-axis direction, and FIG. Fig. 4 is a refractive index distribution chart in the y-axis direction.
FIG. 5 is a diagram showing bending loss characteristics by polarization calculation and measurement, FIG. 5 is a diagram showing bending loss characteristics of three kinds of optical fibers obtained by calculation, and FIGS. 6, 7, and 8 are already proposed respectively. It is an explanatory view showing the refractive index distribution of the optical fiber. In the figure, 1 is a core, 2 is a clad, 3 is an elliptical jacket,
4 is support.
Claims (1)
ド、楕円ジャケット及びサポートが設けられている4層
構造を持ち、曲げを印加して実効的に絶対単一偏波動作
が可能となる偏波面保存光ファイバにおいて、中央に対
し条長15mの範囲で外径が±20〜30μmの間で変化する
ように、光ファイバ外径を連続的に一様に変化させたこ
とを特徴とする楕円ジャケット型偏波面保存光ファイ
バ。1. A polarization structure which has a four-layer structure in which a clad, an elliptical jacket, and a support are sequentially provided around the core around the core, and bending is applied to enable effective absolute single polarization operation. In a wavefront-maintaining optical fiber, an ellipse characterized by continuously changing the outer diameter of the optical fiber so that the outer diameter changes within ± 20 to 30 μm within a range of a strip length of 15 m from the center. Jacket-type polarization-maintaining optical fiber.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP63172568A JPH0774845B2 (en) | 1988-07-13 | 1988-07-13 | Elliptical jacket type polarization-maintaining optical fiber |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP63172568A JPH0774845B2 (en) | 1988-07-13 | 1988-07-13 | Elliptical jacket type polarization-maintaining optical fiber |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH0223305A JPH0223305A (en) | 1990-01-25 |
JPH0774845B2 true JPH0774845B2 (en) | 1995-08-09 |
Family
ID=15944249
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP63172568A Expired - Lifetime JPH0774845B2 (en) | 1988-07-13 | 1988-07-13 | Elliptical jacket type polarization-maintaining optical fiber |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH0774845B2 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5502954A (en) * | 1993-07-21 | 1996-04-02 | Tokyo Automatic Machinery Works, Ltd. | Flap folding device of wrapping machine |
FR2782391A1 (en) | 1998-08-13 | 2000-02-18 | Alsthom Cge Alcatel | Shifted dispersion single mode fibre optic index doping technique; has central triangular, rectangular or trapezoidal profile and outer sheath region with specific inner doped region and higher doped outer region sections |
US10843290B2 (en) * | 2015-01-19 | 2020-11-24 | Weatherford Technology Holdings, Llc | Acoustically enhanced optical cables |
-
1988
- 1988-07-13 JP JP63172568A patent/JPH0774845B2/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
JPH0223305A (en) | 1990-01-25 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
KR910000718B1 (en) | Optical fiber for propagating single mode single polarized wave | |
JP3497298B2 (en) | Optical fiber filter | |
US11353655B2 (en) | Integrated optical polarizer and method of making same | |
JP2594771B2 (en) | Low loss dual mode optical fiber compensator | |
Shao et al. | Seven-core fiber based in-fiber Mach–Zehnder interferometer for temperature-immune curvature sensing | |
JPH0774845B2 (en) | Elliptical jacket type polarization-maintaining optical fiber | |
JPS6360411A (en) | Optical fiber for maintaining plane of polarization | |
JPH08233583A (en) | Optical fiber coil | |
JPS6053285B2 (en) | Constant polarization optical fiber | |
EP0059644B1 (en) | Optical gyroscope | |
RU2188443C2 (en) | Process of manufacture of radiation input-output device in ring interferometer of fiber-optical gyroscope based on special twin light guide | |
JPH0685005B2 (en) | Constant polarization fiber and manufacturing method thereof | |
JP3006205B2 (en) | Optical fiber polarizer | |
Shi et al. | Bias of a resonator fiber optic gyro composed of a polarization-maintaining fiber ring resonator with the photoinduced birefringent grating | |
RU2250482C1 (en) | Polarizing single-mode light guide | |
Mao et al. | Mode excitation theory and experiment of single-mode fiber directional coupler with strong coupling | |
JPH0830774B2 (en) | Elliptical jacket type polarization-maintaining optical fiber | |
JP2528094B2 (en) | Fiber type polarizer | |
JPS6310403B2 (en) | ||
RU2223522C2 (en) | Single-mode single-polarization light guide | |
JPS62283304A (en) | Absolute single polarizing plane maintaining optical fiber | |
JPS61165633A (en) | Method for measuring coupling length of polarization surface preserving optical fiber | |
JPS63300906A (en) | Optical fiber rotational angular velocity meter | |
JPH0518045B2 (en) | ||
JPH01178904A (en) | Single mode optical fiber directional coupler |